Low-Frequency Noise in Supported and Suspended MoS2 Transistors

Abstract

Sensitivity of sensors, the phase noise of oscillators, and intrinsic device performance at the nanoscale are primarily limited by fluctuations in resistance at low frequencies, also called flicker noise. These intrinsic fluctuations in resistance become more prominent in two-dimensional materials due to their ultrathin nature. Here, we report the low-frequency noise (LFN) behavior of supported and suspended MoS2 FETs. Carrier-number fluctuation mechanism was found to be responsible for LFN in both configurations. The extracted frequency index ( $\gamma $ in 1/ ${f}^\gamma $ ) indicates the different trap time constants and mechanisms responsible for LFN in MoS2 transistors. A $\gamma $ value of 2 in suspended transistors indicates a tight trap time-constant distribution likely due to recombination–generation through trap states arising only from intrinsic defects and/or extrinsic adsorbates. A wide time-constant distribution ( $\gamma \!\sim \textsf {1}$ to 1.4) in supported transistors indicates the presence of various kinds of traps, such as adsorbates, intrinsic defects, as well as interface and oxide traps. Furthermore, variation in S0 (characterizes the magnitude of noise) with gate voltage in both supported and suspended device configurations was validated analytically using the carrier-number fluctuation model.